1. Field of the Invention
The present invention relates to a method and system for delivering and receiving data, and a data delivery and data reception mechanisms therefor. More particularly, the present invention relates to a method and system for controlling data delivery and reception in an environment where at least one management system collects and manages data and at least one terminal station connects to said at least one management system to make access to the data stored therein. The present invention further relates to a data delivery and data reception mechanisms to be implemented as part of the above system, and also to a data delivery and reception system based on the Internet or other on-line services, in which servers (or management systems) provide their clients (or terminal stations) with information delivery services.
2. Description of the Related Art
Monitoring data traffic on a network and activities of network devices is one of the important functions of network management. Typically, in a distributed network management environment, a plurality of management systems collect operational status information concerning their respective network subsystems and maintain the collected information in their local storage. Network operators at remote locations perform administrative actions to control the entire network, making access to the information stored in the management systems through their local terminal stations.
In conventional network management systems, status changes and critical events occurred in a subsystem are reported to its local management system in the form of status messages with appropriate timestamp information indicative of their occurrence times. Upon receipt of such status messages, the recipient management system saves the received data into its storage unit, and if required, rearranges the collected data records in the order of their occurrence times. Terminal stations are allowed to make a connection to the management system at any time they need the delivery of data records stored therein. The management system responds to this data delivery request by returning the latest data records to the requesting terminal stations. Note here that the management system keeps a log of what data records are delivered to which terminal station. Next time it receives a data delivery request from the same terminal station, the management system selectively sends undelivered data records to the terminal station by referring to the log information.
A first problem with the above-described conventional systems is that event occurrence timestamps affixed to the status messages are based on each subsystem""s local clock. Such local clocks may not always be accurate enough, and it is hard to guarantee their synchronization. Because of this limited reliability, the data rearrangement based on the event occurrence timestamps could result in an incorrect sequence of data records.
To solve this problem, some conventional management systems use time offset data to compensate for the chronological differences among subsystems. They rearrange the collected data records after making a correction to the original event occurrence timestamps with those time offset data. This technique, however, requires the management systems to spend more processing resources.
Another problem with the conventional management systems is that they have to maintain a log of what data records have been delivered to which terminal station. This task consumes much storage space in the management systems, besides imposing more workloads on them. That is, higher-class computers are required as the management system platforms.
Taking the above into consideration, an object of the present invention is to provide an improved method and system for controlling data delivery and reception, which makes it possible to alleviate the processing workloads imposed on management systems and reduce the hardware and software resources required in management systems.
To accomplish the above object, according to the present invention, there is provided a system for controlling data delivery and reception in such an environment where at least one management system collects and manages data and at least one terminal station connects to said at least one management system to make access to the data stored therein. This data delivery and reception system comprises the following elements: (a) a data storage unit, disposed in the management system, to store data records together with reception timestamps indicative of the time when each data is received by the management system; (b) a data requesting unit, disposed in the terminal station, to send a request to the management system to deliver the data records, the request including a time specification for qualifying the data records to be delivered; (c) a data retrieval unit, disposed in the management system and responsive to the request sent from the data requesting unit, to retrieve, out of the data storage unit, relevant data records whose reception timestamps are not earlier than the time specification included in the request; (d) a data transmission unit, disposed in the management system, to transmit to the terminal station the data records retrieved by the data retrieval unit, together with a transmission timestamp; (e) a timestamp storage unit, disposed in the terminal station, to store the transmission timestamp sent together with the data records from the data transmission unit; and (f) a data reception unit, disposed in the terminal station, to receive the data records sent from the data transmission unit.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate a preferred embodiment of the present invention by way of example.